There are two constraints on any functionalist solution to the Mind-Body Problem construed as an answer to the question, “What is the relationship between the mental properties and relations (hereafter, simply the mental properties) and physical properties and relations?” The first constraint is that it must actually address the Mind-Body Problem and not simply redefine the debate in terms of other, more tractable, properties (e.g., the species-specific property of having human-pain). Such moves can be seen to be spurious by the very multiple-realizability intuitions that motivate functionalism in the first place. For, according to those intuitions, it is possible for a being to experience pain, have beliefs, etcetera, and yet not only to be of a different species, but to have an entirely different material constitution from human beings